Typical snowplow systems designed to be mounted on smaller vehicles, such as pickup trucks or sport utility vehicles, operate by providing a plow blade pivotally mounted on a support arm which, in turn, is pivotally mounted to the vehicle frame. A first mechanism is used to raise or lower the plow by causing the support arm to pivot around an axis proximate the vehicle. This first mechanism is usually a hydraulic piston assembly or, in simpler cases, an electric winch. While plowing, the plow is in a lowered position and can pivot around a horizontal axis defined by a hinge which connects the plow to the distal end of the support arm. A spring or similar biasing mechanism extends from an attachment point on the support arm to another attachment point on the top of the plow. The spring controls the rotation of the plow around its axis of rotation by biasing the lower, leading edge of the plow in a forward direction. In the event that the plow contacts a relatively immovable object, the plow is allowed to rotate around its hinge such that the leading edge rotates rearwardly, thereby stretching the spring. Once the object has passed under the leading edge, the spring pulls the top edge of the plow back, thereby rotating the leading edge forward to its normal operating position. This damping feature protects the vehicle frame from encountering excessive forces during a plowing operation.
Rudimentary systems rely on the weight and shape of the plow to provide the downward force necessary to keep the plow close to the ground during operation. More advanced systems have additional measures for providing downward force. Such force is desirable when using a plow to scrape hard-packed snow and ice from a road""s surface. Providing such a downward force must be done in a controlled manner to prevent injury to the plow and vehicle. Existing systems utilize hydraulic pressure sensors in order to maintain a predetermined downward pressure on the blade of the plow. Unfortunately, there are many problems pertaining to the complexity of these systems.
Existing hydraulic systems must be installed on the carrier vehicle at the factory while the vehicle is being assembled. Their complexity and structural requirements preclude them from being added to existing vehicles as an after-market retrofit. Therefore, a decision must be made at the time the sport utility vehicle or pickup truck is being purchased as to whether it will ever be used as a snowplow.
In addition to this installation limitation, the complexity of existing hydraulic systems renders them costly and unreliable. They incorporate special hydraulic manifolds that typically include expensive pressure sensors to monitor the downward force exerted by the plow blade. These complicated sensors have problems with leakage and also tend to exhibit inconsistent performance at varying temperatures. Because they monitor the pressure of the hydraulic manifold, they become inaccurate when the hydraulic fluid changes viscosity due to temperature fluctuations. Furthermore, the valve body used to maintain the pressure must be designed to accommodate these sensors. This complex valve does not allow the plow operator to adjust the preset amount of downward pressure exerted by the blade. This becomes problematic when the plow is used to clear light snow from softer surfaces such as dirt roads.
Also, the existing hydraulic systems necessarily include a significant number of electrical wires extending from the sensors to the plow control system. These wires are susceptible to breaking and corrosion. As snowplows are used in cold environments and typically come into contact with corrosive salts, minimizing the number of electrical wires exposed to these harsh conditions would be beneficial.
It can be seen that there is a need for a reliable plow system which places a user-selected downward force on the plow blade.
Additionally, there is a need for a plow system which can be easily mounted on the front or rear of a sport utility vehicle or light truck as an after-market addition.
There is also a need for a plow system which is minimally susceptible to electrical failure due to wire breakage and corrosion.
There is yet a further need for a plow system which can be controlled and adjusted from the cab of the carrier vehicle.
The various embodiments of the present invention pertain generally to a plow system which includes a control system that monitors the downward pressure exerted by the blade as a function of the spatial relationship between the vehicle frame and the ground. As the downward pressure of the blade increases, the front of the vehicle is lifted somewhat, relieving some of the weight the vehicle places on its front suspension, thereby increasing the distance between the vehicle frame and the ground or an object substantially fixed relative to the ground, such as the front axle or wheel. The relative simplicity of this system allows it to be added to the front or the rear frames of existing sport utility vehicles or light trucks. Additionally, by constantly monitoring the performance and position of the vehicle""s front suspension, the system lends itself to the inclusion of limit or overload measures to ensure the suspension will not be damaged during operation of the plow.
One embodiment of the present invention includes a telescoping sensor linkage attached to the frame of the carrier vehicle with an upper bracket. The linkage is directed downwardly and abuts against a lower bracket which is fixed relative to the vehicle""s front axle. The telescoping sensor linkage is constructed and arranged to sense and measure changes in the distance between the upper bracket and the lower bracket and sends this information, either mechanically or electronically, to a plurality of micro switches. The micro switches are operably attached to valve controllers which control the flow of hydraulic fluid through the hydraulic cylinders. One of these micro switches, then, can be designated as a pressure increase switch while the other can be designated as a pressure decrease switch. Alternatively, more than two micro switches may be used. For instance, it may be desirable to use four micro switches to provide redundancy in the event that one or both of the other micro switches malfunctions. It may also be desire to designate two of the micro switches for use in a relatively light plowing operation such as light snow, and designate the other two micro switches for use during heavier operation such as plowing heavy snow and ice, spreading gravel, or grading operations.
The distance between the upper and lower brackets of this embodiment is representative of a load placed on the suspended frame of the vehicle. It is understood that the device could be constructed and arranged to measure the distance between the suspended frame and the ground, however, the inclusion of a lower bracket provides a relatively clean surface against which the telescoping sensor can act. Such a mechanical sensor measuring distance to the ground by actually coming in contact therewith, would likely encounter obstacles such as snow and ice during operation, and would render such a configuration impractical.
Another embodiment of the present invention includes an electronic proximity sensor, similarly mounted to the vehicle frame, and directed toward a lower mounting bracket which provides a flat, horizontal target against which the proximity sensor may measure distance. Though it is envisioned that the proximity sensor could be directed at the ground and measure distance therefrom, the bracket provides a surface which is free from irregularities and, therefore, would provide a more accurate indication of the front-end loading the vehicle is experiencing due to the downward pressure of the plow.
The electronic proximity sensor is electrically connected to an electronic control box which accepts data from the proximity sensor and uses it to control the flow of hydraulic fluid in the cylinder used to control the vertical position of the plow blade. The electronic control box also provides data to the vehicle operator who can then adjust the downward pressure of the blade and the mode of operation thereof, from the cab of the carrier vehicle.
Another embodiment uses a variable resistor to convert the mechanical reading of changes in the elevation of the frame to an electrical representation. A mechanical linkage, such as that described above, is operably connected with a potentiometer or variable resistor so that when the frame moves up and down, the current flowing out of the variable resistor changes, thereby providing a current to a control system having fluctuations representative of the changes in elevation of the frame.
It is further envisioned that the various embodiments of the present invention provide multiple modes of operation of the plow blade. One such mode of operation is a xe2x80x9cfloatxe2x80x9d mode. While operating in the float mode, the valves porting fluid to either side of the hydraulic cylinder are left open, allowing it to move freely, so that the weight of the plow may be used to provide the necessary down pressure. As the plow blade encounters contours in the road surface, the hydraulic fluid is allowed to flow between other sides of the hydraulic cylinder, thereby allowing the plow blade to raise or lower as necessary and xe2x80x9cfloatxe2x80x9d over the surface of the road. In this mode of operation, the proximity sensor may be used as an overload protection device. If an extreme contour is encountered, the sensor would detect an abrupt change in the load on the vehicle""s suspension, activate the hydraulic pump, and close the ports to the cylinder as necessary to raise or lower the plow blade.
Another such mode of operation is the xe2x80x9cdown pressurexe2x80x9d mode. The vehicle operator selects a desired amount of pressure that he or she wants the blade to be putting on the surface being plowed. This amount of pressure will correspond to a distance between the suspended vehicle frame and elevation which is relatively fixed to the ground such as that of a wheel or an axle. That distance is then monitored and corrections are made to the elevation of the snowplow such that the set distance or load on the vehicle""s suspension is maintained during operation.
Another such mode of operation is a manual operation mode. Manual mode may be desired when various levels of ice buildup exist on a relatively flat surface and it is desired to use the plow blade to scrape the ice off of the surface, regardless of load. Another application of manual mode may be when it is desired to leave a gap between the bottom of the plow and the hard ground such as may be the case when using the plow to spread a layer of gravel or other granular material. A switch is provided for this mode of operation which allows the operator to raise and lower the blade to a certain elevation and sufficiently fix the height of the blade, relative to the vehicle, during operation. A plurality of operator control configurations are envisioned and described in more detail herein.